Distinct mechanisms controlling rough and smooth endoplasmic reticulum contacts with mitochondria

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Study of Endoplasmic Reticulum and Mitochondria Interactions by In Situ Proximity Ligation Assay in Fixed Cells
09:34

Study of Endoplasmic Reticulum and Mitochondria Interactions by In Situ Proximity Ligation Assay in Fixed Cells

Published on: December 10, 2016

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Peter T C Wang1, Pierre O Garcin2, Min Fu1

  • 1Departments of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.

Journal of Cell Science
|June 13, 2015
PubMed

Insights

Gp78 protein regulates endoplasmic reticulum and mitochondria connections by degrading mitofusins. Autocrine motility factor binding to Gp78 influences these interactions, impacting cell functions.

Area of Science:

  • Cell Biology
  • Mitochondrial Dynamics
  • Endoplasmic Reticulum Function

Background:

  • Gp78, an ER-associated degradation E3 ubiquitin ligase, interacts with mitochondria.
  • Gp78 targets mitofusins (Mfn1, Mfn2), key mitochondrial fusion proteins, for degradation.
  • Gp78 functions as the cell surface receptor for autocrine motility factor (AMF).

Purpose of the Study:

  • To investigate the role of Gp78 and AMF in regulating ER-mitochondria contacts.
  • To determine how mitofusins influence ER-mitochondria interactions.
  • To elucidate the mechanisms controlling ER-mitochondria Ca(2+) coupling.

Main Methods:

  • Utilized short hairpin RNA (shRNA) to knock down Gp78 expression.
  • Employed small interfering RNA (siRNA) to knock down Mfn1 and Mfn2.
  • Performed electron microscopy to visualize ER-mitochondria contacts in HT-1080 fibrosarcoma cells.
  • Administered autocrine motility factor (AMF) to assess its effects.

Main Results:

  • Gp78 knockdown and AMF treatment selectively reduced rough ER (RER)-mitochondria contacts.
  • Smooth ER (SER)-mitochondria contacts were unaffected by Gp78 knockdown or AMF.
  • Mitofusin 1 knockdown increased SER-mitochondria contacts, while Mfn2 knockdown increased RER-mitochondria contacts in Gp78-depleted cells.
  • Mitofusins were found to inhibit ER-mitochondria interactions.

Conclusions:

  • Gp78-mediated degradation of Mfn2 is crucial for regulating RER-mitochondria contacts in response to AMF.
  • Mfn1 regulates close SER-mitochondria contacts.
  • These findings reveal novel mechanisms governing ER-mitochondria interactions and Ca(2+) coupling.
Keywords:
AMFCa2+ couplingER-mitochondria contactsGp78 E3 ubiquitin ligaseMitofusin

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